1. Field of the Invention
The present invention relates to an arc gas venting structure of an air circuit breaker, and in more detail, to an arc gas venting structure of an air circuit breaker which easily discharges an arc gas, which is generated when a movable contact and a fixed contact are separated, to the outside.
2. Discussion of Related Art
Generally, an air circuit breaker is a sort of a circuit breaker which breaks a current when power is transmitted and mutated, an electric circuit and the like makes or breaks a load, or an accident such as grounding, short-circuit, or the like occurs, and is generally used for a low-pressure apparatus.
The air circuit breaker includes a switching mechanism which opens and closes a fixed contact and a movable contact, an over current relay which detects a fault current and outputs a trip command to break an inflow of a high current, and a mechanical trip device which is disposed between the switching mechanism and the over current relay and generates and transmits a mechanical operation force to the switching mechanism when the over current relay outputs the trip command.
Meanwhile, FIG. 1 is a perspective view of a conventional air circuit breaker, FIG. 2 is a front view illustrating a relay provided at the conventional air circuit breaker and a trip device connected thereto, and FIG. 3 is a perspective view illustrating the relay provided at the conventional air circuit breaker and the trip device connected thereto.
As shown in FIGS. 1 to 3, the air circuit breaker includes a body 1 which forms an accommodation space therein and a cover 2 coupled to a front of the body 1.
In the body 1, a fixed contact (not shown) and a movable contact, to which a bus bar and a load are connected, and a switching mechanism (not shown) which opens and closes the fixed contact and the movable contact are accommodated and installed.
Also, an arc quenching portion 4 is provided above the body 1 to vent an arc generated when the fixed contact and the movable contact are separated.
In addition, an over current relay 3, which detects a fault current or an over current and detects and breaks an inflow of a current which has a value higher than a preset current value when the current flows thereinto, is provided in front of the body 1. The cover 2 has an opening such that a front of the over current relay 3 is exposed.
Here, since the over current relay 3 performs important functions of detecting a fault current and outputting a trip command, periodic checkup and replacement are necessary.
Also, since it is impossible to perform functions of detecting a fault current and generating a trip command when the over current relay 3 is separated to be checked up or replaced, a separation is performed while a trip button is pushed such that the switching mechanism performs a trip operation.
Meanwhile, the over current relay 3 is assembled with a trip device 5 and transmits a trip command to the trip device 5 when the over current relay 3 detects an over current and a fault current.
Here, the switching mechanism performs a sending (ON) operation for applying an electric current or a trip (OFF) operation for breaking an electric current through the trip device 5.
That is, the over current relay 3 is used for detecting an over current and a fault current of the air circuit breaker, and the trip device 5 operates the switching mechanism to trip (OFF) the air circuit breaker according to a command given by the over current relay 3.
However, in the conventional air circuit breaker configured as described above, when the switching mechanism is operated by the over current relay 3 to break the fault current, it is necessary to vent an arc gas, which is generated when the movable contact and the fixed contact are separated, to the outside through the arc quenching portion 4. However, an internal pressure of the arc quenching portion 4 rapidly increases in a short time due to the arc gas. Also, due to the increase in the internal pressure of the arc quenching portion 4, the arc gas leaks into the trip device 5 and the over current relay 3 such that components of the trip device 5 and the over current relay 3 are seriously damaged due to a pressure of the arc gas.
Also, since the components of the trip device 5 and the over current relay 3 are damaged, an error occurs during operation when the air circuit breaker is used for a long period of time.